citanon wrote:I don't think any of the manufacturers project that ADVENT would give the F35 supercruising performance like the F22. They project better range, higher sustained speed at low altitude due to better cooling, and better acceleration but not significantly higher speed at military thrust levels.

I could be wrong (if so please give a link).

This is a gross simplification but remember that aerodynamic drag scales as the square of the velocity. It takes a lot of extra thrust to change your drag limited top speed from < mach 1 to mach 1.8. .

From what I have read, there is a component that goes as the square, but it is multiplied by another factor that falls from Mach 1 to Mach 1.5 or so.If the new engines aren’t being designed to let the F-35 supercruise, it is because that isn’t a priority.

Einstein got it backward: one cannot prevent a war without preparing for it.

A) the B-21 is a clean sheet designB ) the PCA (or whatever it is eventually called, is a clean sheet design.)C ) the engine upgrades for the F-35, will definitely provide improved acceleration, range, persistence. They may very well improve cruise speed/max speed, too. They won't give the F-35 supersonic performance like the F-22, but its subsonic/transonic performance should be on par/superior to any competitors or threats.

I think a very large aspect of the F-22's dominance in the supercruise areas is the Mil power T/W ratio it has. At .80 nothing other than the Typhoon (at .76) is even close. Most other fighters are in the mid to high .60s. The F-35 with it's massive fuel fraction is only .57 (comparable to other high fuel fraction aircraft) and when we match the F-22's 28% fuel fraction we are at a mil T/W of .65. FOr a engine upgrade to give the F-35 the power (so not counting other things) to supercruise well it needs to deliver around the 35,000lbs mark. If the F135 block 1 upgrade is on the higher end of it's power increase curve then it's already got a 31,000lbs option. Advent has to add another 3,000-4,000lbs of dry thrust for it to get closer to the F-22's mil T/W ratio. When that happens I could see the F-35 being decent at supercruising @1.4-1.5 mach at altitude. If advent can provide that type of performance upgrade and capability then I think the F-35 would serve the Japanese and all of it's other users in the Air defense role quiet well, plus all the advantages variable cycle brings for the main strike role and subsonic cruise power. I would venture a guess if the F-22 had more Al-31 style engines with large afterburner numbers but small mil power numbers it's supercruise would be far more limited.

But another significant factor apart from engine power is the aerodynamic configuration. A large amount of effort on the design evolution of the F22 was devoted to reducing drag, and supersonic drag was a particularly vexing problem.

The prototype design was unfrozen at the last minute in May 1988 after the Air Force eliminated the requirement for thrust reversing for short-field operations. The change allowed the team to alter the external mold lines on the aft fuselage and nozzles in the area around the thrust reversers. The trimmed aft end reduced drag significantly. "We never had an airplane with the right supersonic drag until May," Mullin explains. "We scared the Air Force when we unfroze the prototype design at that late date. The supersonic drag was still too high to supercruise. A team led by Ed Glasgow, our chief flight sciences engineer, redesigned the forebody and aftbody. Suddenly we had acceptable supersonic drag levels that ensured that the airplane would supercruise."

The F35 as it stands is optimized for trans sonic performance. For starters it has less wing sweep. For efficient supercruise, its aerodynamic configuration would likely need significant revisions.

geforcerfx wrote:I think a very large aspect of the F-22's dominance in the supercruise areas is the Mil power T/W ratio it has.

Eh I think mil power T/W isn't a particularly good comparison. For example, the Gripen NG supposedly supercruises using an engine with 13,000 lb of mil thrust (unless the engine plans have changed in the meantime), weighing 17,600 lb empty with 7500 lb of internal fuel capacity. At 28% fuel fraction, the T/W is just 0.53, and that's assuming no weapons; weapons would decrease the T/W further.

geforcerfx wrote:I think a very large aspect of the F-22's dominance in the supercruise areas is the Mil power T/W ratio it has.

Eh I think mil power T/W isn't a particularly good comparison. For example, the Gripen NG supposedly supercruises using an engine with 13,000 lb of mil.

Why does everyone quote that number? The F414-GE-400 produces 14,327 lbs of thrust in military power. As far as supercruise, SAAB can claim whatever they want, it will be interesting to see them demonstrating that outside of the cold, dry air of Sweden when loaded for a mission.

geforcerfx wrote:I think a very large aspect of the F-22's dominance in the supercruise areas is the Mil power T/W ratio it has.

As above from vanshilar - Supercruise is top speed in mil power - so drag is what you need to look at not weight (Max aero speed is when Thrust == Drag). Spurts listed some figures in Strike Fighters v2 (2016) for drag area.

Other major factor - F-22 likely retains higher relative dynamic thrust as you go higher due to having a lower bypass ratio engine.

I would venture if F135 requires the same intake size as two F414, the F-135 would still be better due to less drag from a larger single face. The smaller the engine face the more resistance to flow. And since flow restriction is exponentially related to overall size, it wouldn't be a tiny difference. Maybe by the time you hide the front face of the turbine it becomes less of a factor, but actual flow through the engine would be significantly less impeded on the single larger engine, giving an edge in efficiency.

It will be a new airframe, but one which a lot of work has already been done on...

It will be much larger than the F-22 (think fuselage plugs), be much faster and of course have much greater range. Entire missions will be able to be flown in super-cruise. Hell that was done 25 years ago WITHOUT ADVENT engines. It will be much stealthier, and have more room for F-35 like sensors. This aircraft has already been built, flown, tested and found to be the best fighter America never put into production. But it's coming back, because you're right - starting with an F-22 OR F-35 airframe is half assing it. We don't need to, we already have something "new" waiting in the wings.

And finally, finally, the design team that created her will be vindicated....

where it says the Gripen E has >64 kN of thrust in military power. If so, are you sure that's based on currently available thrust, versus what they project to have following unspecified technical developments? After all, that document also says the max takeoff weight is now 17,000 kg when it used to be 16,500 kg, and 16,000 kg before that.

No, I’ve gotten the thrust figures from several different studies (one in particular, from RAND about military turbofan development had manufacturer or USAF figures on nearly every current fighter engine, except the one everyone would like to know). My guess is that most sites applied the old 60% rule of thumb: 22,000lbs thrust class engine ~ 13,000lbs thrust military power. Works well enough in general but the F414 has a low bypass ratio.

Their cash cow is the F-35. They know it. The air force knows it. Everybody knows it. But they raised the ghost of the F-22 for a reason.. What could it be? I suspect to get a leg up on PCA...

Think about it: It'd be a nice lead in project for them. Allegedly the Air Force wants existing/off the shelf technologies to shorten the PCA's developmental cycle. A lot of that would be found in this F-22/F-35 hybrid, and they'd be doing it on Japans dime. Yes, we've allocated a lot to study/design PCA. But every dollar LM saves in applying lessons learned from this hybrid is a dollar earned. They'd be able to offer a finished PCA at a discounted price with technologies and manufacturing techniques refined here.

What do you think? I think it'll for sure give them a leg up vs. Boeing and any other PCA competition...

If Japan's required specs simply cannot be met by the F-35, then LM has no choice but to offer that. IIRC the two that I can remember are Japanese engines and radars. On top of that, cost may be an issues that forces LM to either hybridize or propose a lesser fighter as a clean-sheet design.

Remember that the costliest item v(in time and money) to develop was the avionics and that can be easily brought over from the F-35 (except for the required Japanese radar).

Japan is not going to fund an F-22/F-35 Hybrid. Hell, they are lucky to be able to afford a modest number of F-35's each year. Which, she must have to counter the current and projected Chinese Threats from the PLAAF and PLAN. (i.e. J-20 and J-31)

As I have said over and over again. The most likely course is Japan will continue to purchase F-35's into the coming decade. While, joining with a future 6th Generation Program in another decade or so. Which, likely would be the F-X (USAF) or NGAD (USN) Programs from the US. Of course we are at the very early conceptual stages. So, we have a very long ways to go.....